The present invention relates to a machine and method for the automated trimming of fish fillets, including the removal of undesired tissue, for example fat tissue, discoloured tissue and any other undesired portions of a fish fillet.
Fish of the salmon family are characterized in that fatty tissues are quite distinct in relation to the meat. After the fish has been filleted, a significant amount of fatty tissues, discoloured tissues as well as fins and bones must be removed in order to achieve a quality product. During the initial filleting process, the head and backbone are removed from the fish, and the fish is divided into two fillets. U.S. Pat. No. 5,591,076 discloses an apparatus for the automatic processing of whole flatfish, wherein the dorsal and ventral fins are removed from the fish. This known device does not, however, provide for the trimming of fatty tissues from the resulting fillets.
Various attempts have been made at the automatic removal of fatty tissues from the surface of fish fillets. These attempts have heretofore provided unsatisfactory results. Consequently, the trimming of fish fillets continues to be done manually.
It is generally known to use a freezing drum to remove the skin and the fatty layer immediately beneath the skin from a fish fillet. In devices of this nature, the fillet is frozen skin-side down to the drum. A horizontal band knife is then used to slice the fillet, leaving the skin and the layer of fat attached to the drum. While this technique is adequate for removing the skin, it is unsatisfactory for the removal of layers of fat from the opposite side of the fillet. This is because the meat-side of the fillet does not have a flat profile, as is the case with the skin side. On the meat-side of the fillet, the dorsal edge and the ventral edge (which both contain layers of fat) are significantly lower than the thickest region of the fillet. The above-described technique would thus remove an excessive amount of meat from this thick portion.
The machine from U.S. Pat. No. 5,779,531 attempts to solve this problem by providing rollers that press the fillet against a conveying surface in order to flatten the fillet.
Again, this technique is intended primarily to remove the surface layer from the skin-side of the fillet, and is incapable of flattening the fillet to the degree necessary for the effective removal of fatty tissues from the meat-side.
It is known to use devices comprising brushes to remove fat from the meat-side of a fillet, however machines of this type produce a rough and unattractive surface.